An area of low barometric pressure, with its attendant system of winds. Also called a depression or cyclone.

The record or trace made by a microbarograph.

A type of wind vane having a split or V-shaped tail. The apex orients itself to the direction of the wind.

The general term for dry atmospheric suspensoids, including dust, haze, smoke. and sand. Compare to hydrometeor.

Precipitation of white, opaque, spherical or conical ice particles that are crisp and easily crushed and that have diameters of 2 to 5 mm.

The scientific study of the waters of the earth, especially with relation to the effects of precipitation and evaporation upon the occurrence and character of water in streams, lakes, and on or below the land surface. In terms of the hydrologic cycle, the ...

A spring which is designed to achieve a fixed spring constant over a wide temperature range. Usually, this involves an alloy with high nickel content such as Ni-Span C. It is common for these springs to be stress relieved at elevated temperature after for ...

Wind with a speed between 34 and 40 knots (39 and 46 mph); Beaufort scale number 8.

Anemometer whicb measures wind speed by measuring the degree of cooling of a metal wire heated by an electric current. A type of cooling power anemometer.

A unit of pressure which directly expresses the force exerted by the atmosphere. Equal to 1000 dynes/cm2 or 100 pascals.

variable audio-modulated radiosonde developed at the Bureau of Standards and used by the United States weather services.

A liquid-in-glass thermometer which uses an organic substance such as alcohol as the thermometer liquid. This type of thermometer has a low freezing point and a high coefficient of expansion. It is less accurate, however, than a mercury thermometer.

Thermometer for measuring the temperature in the soil at different depths.

The actual lifting force of an inflated balloon, usually expressed in grams.

A type of recording siphon barometer. The mechanically magnified motion of a float resting on the lower mercury surface is used to record atmospheric pressure on a rotating drum.

A faintly-colored circular arc similar to a rainbow but formed on fog layers containing drops whose diameters are 100 microns or less. Also called mistbow, white rainbow.

A device that allows a terminal or computer at one location to communicate with a terminal or computer at a distant location via wire or phone lines.

Phase Shift Keying. A form of phase modulation of a data signal performed by a modem for transmission over dedicated wire or phone lines.

The time required for an instrument to registe 63.2% of a step change in the variable being measured.

The upward force produced by the gas in a balloon. It is equal to the free lift plus the weight of the balloon and the attached equipment.